Ulthera treatment uses ultrasound to warm the skin and the underlying musculoaponeurotic fascia (Thin layer of muscle and fibrous tissue).
The ultrasound also projects on a screen the image of the tissues that it treats.
The operator is not supposed to treat the area containing the thyroid gland (Minimal musculoaponeurotic layer), although there are rare cases where the thyroid can prolong itself in the areas being treated. Most likely, in this case,if any thyroid tissue gets ultrasound waves, nothing untoward will happen.
Under no circumstances should these statements be considered specific medical advice. Please make sure you discuss this matter with your Internist.